In the oil and gas industry, refracturing operations are conducted to re-stimulate existing wellbores. Such operations typically require the isolation of existing perforations. In one method, a casing liner is run downhole to block all or a portion of existing perforations. In another method, fluids are pumped into the existing perforations to provide a temporarily restricted flow path into those zones.
These conventional methods have drawbacks. For example, the use of fluids to temporarily restrict the zones does not provide complete isolation of the existing perforations. As a result, during re-stimulation of the new perforation clusters, some fluids are lost into the existing perforations. This phenomenon is especially troublesome for tight formations which is require higher treating pressures. Also, the casing liners used to block all or a portion of the perforations are typically permanent installations, thus resulting in zones that can no longer be produced—and those casing liners that can be removed require expensive and dangerous removal operations. Moreover, the use of permanent casing liners typically results in a smaller flow diameter which limits the treatment rate during the stimulation service.